Trachea and bronchi: topography, structure, functions, blood supply, innervation, regional lymph nodes. Anatomy of the major bronchi Topography of the major bronchi

Bronchi Trachea(windpipe) - an unpaired organ (10-13 cm), which serves to pass air into the lungs and back, begins at the lower edge of the cricoid cartilage of the larynx. The trachea is formed by 16-20 half rings of hyaline cartilage. The first half-ring is connected to the cricoid cartilage by the cricotracheal ligament. The cartilaginous half-rings are connected to each other by dense connective tissue. Behind the rings there is a connective tissue membrane (membrane) mixed with smooth muscle fibers. Thus, the trachea is cartilaginous in front and on the sides, and connective tissue in the back. The upper end of the tube is located at the level of the 6th cervical vertebra. The lower one is at the level of 4-5 thoracic vertebrae. The lower end of the trachea divides into two main primary bronchi, the site of division is called the tracheal bifurcation. Due to the presence of elastic fibers in connective tissue between the semirings, the trachea can lengthen when the larynx moves up and shorten when it moves down. The submucosal layer contains numerous small mucous glands.

Bronchi are a continuation of the windpipe, both functionally and morphologically. The walls of the main bronchi consist of cartilaginous half-rings, the ends of which are connected by a connective tissue membrane. The right main bronchus is shorter and wider. Its length is about 3 cm, consists of 6-8 half rings. The left main bronchus is longer (4-5 cm) and narrower, consisting of 7-12 half rings. The main bronchi enter the gate of the corresponding lung. The main bronchi are the bronchi of the first order. From them depart bronchi of the 2nd order - lobar (3 in the right lung and 2 in the left), which give rise to segmental bronchi (3 orders), and the latter branch dichotomously. In the segmental bronchi there are no cartilaginous half-rings; the cartilage breaks up into separate plates. The segments are formed by pulmonary lobules (up to 80 pieces in 1 segment), which include the lobular bronchus (8th order). In small bronchi (bronchioles) with a diameter of 1-2 mm, cartilaginous plates and glands gradually disappear. Intralobular bronchioles break up into 18-20 terminal bronchioles with a diameter of about 0.5 mm. In the ciliated epithelium of the terminal bronchioles there are individual secretory cells (Clark), which produce enzymes that break down surfactant. These cells are also the source of restoration of the epithelium of the terminal bronchioles. All bronchi, starting from the main bronchi and including the terminal bronchioles, make up the bronchial tree, which serves to conduct a stream of air during inhalation and exhalation; respiratory gas exchange between air and blood does not occur in them.

Middle mediastinum limited anteriorly by the anterior wall of the pericardium, posteriorly by the posterior wall of the pericardium and the bronchopericardial membrane. The mediastinal pleura forms the lateral walls.

IN middle mediastinum the heart with the pericardium, pulmonary arteries and veins, the bifurcation of the trachea and the main bronchi are located. The esophagus and vagus nerves pass through it into the posterior mediastinum.

Tracheal bifurcation. Topography of the tracheal bifurcation. Main bronchi. Topography of the main bronchi.

After passing behind the aortic arch, the trachea is divided into right and left main bronchi, forming tracheal bifurcation, which is projected onto the IV-V thoracic vertebrae (this level separates the upper mediastinum and the three lower ones). A sharp protrusion into the lumen of the trachea at the site of its division into bronchi is called “ carina trachea", carina tracheae.

Of the two main bronchi the right one is shorter and wider than the left one, and often its direction almost coincides with the direction of the trachea. Because of this foreign bodies much more often they enter from the trachea into the right bronchus (70%).

Depth of the trachea in the chest cavity it increases downwards (if at the sternal notch the trachea is 3-4 cm from the surface of the chest wall, then in the bifurcation area it is 6-12 cm).

Anterior to the tracheal bifurcation and partly from the right main bronchus passes the right pulmonary artery. Below the bifurcation of the trachea is the right atrium, separated from it by the pericardium. Behind the posterior and upper wall of the right main bronchus passes v. azygos, flowing into the superior vena cava. Along the right surface of the trachea in the peritracheal tissue there is n. vagus dexter

Anterior to the left bronchus passes the aortic arch, which bends around it from front to back and passes into the descending aorta. Behind the left bronchus are the esophagus, the aortic arch (the site of transition to the descending aorta) and n. vagus sinister.

In front of this and that bronchus the corresponding pulmonary artery is partially adjacent.

In the loose fiber surrounding tracheal bifurcation And main bronchi, located paratracheal and tracheobronchial The lymph nodes, which are regional for the trachea and bronchi, lung and pleura, esophagus, mediastinal tissue.

Trachea, tracheal bifurcation, main bronchi, the esophagus and the surrounding tissue have a common esophageal-tracheal fascial membrane. Its structure is most dense at the level tracheal bifurcation. From here it descends as the bronchopericardial membrane to the posterior wall of the pericardium.

64. Trachea and bronchi: topography, structure, functions, blood supply, innervation, regional lymph nodes.

Bronchi Trachea (trachea) (windpipe) - an unpaired organ (10-13 cm), which serves to pass air into the lungs and back, begins at the lower edge of the cricoid cartilage of the larynx. The trachea is formed by 16-20 half rings of hyaline cartilage. The first half-ring is connected to the cricoid cartilage by the cricotracheal ligament. The cartilaginous half-rings are connected to each other by dense connective tissue. Behind the rings there is a connective tissue membrane (membrane) mixed with smooth muscle fibers. Thus, the trachea is cartilaginous in front and on the sides, and connective tissue in the back. The upper end of the tube is located at the level of the 6th cervical vertebra. The lower one is at the level of 4-5 thoracic vertebrae. The lower end of the trachea divides into two main primary bronchi, the site of division is called the tracheal bifurcation. Due to the presence of elastic fibers in the connective tissue between the semi-rings, the trachea can lengthen when the larynx moves up and shorten when it moves down. The submucosal layer contains numerous small mucous glands.

Bronchi are a continuation of the windpipe, both functionally and morphologically. The walls of the main bronchi consist of cartilaginous half-rings, the ends of which are connected by a connective tissue membrane. The right main bronchus is shorter and wider. Its length is about 3 cm, consists of 6-8 half rings. The left main bronchus is longer (4-5 cm) and narrower, consisting of 7-12 half rings. The main bronchi enter the gate of the corresponding lung. The main bronchi are the bronchi of the first order. From them depart bronchi of the 2nd order - lobar (3 in the right lung and 2 in the left), which give rise to segmental bronchi (3 orders), and the latter branch dichotomously. In the segmental bronchi there are no cartilaginous half-rings; the cartilage breaks up into separate plates. The segments are formed by pulmonary lobules (up to 80 pieces in 1 segment), which include the lobular bronchus (8th order). In small bronchi (bronchioles) with a diameter of 1-2 mm, cartilaginous plates and glands gradually disappear. Intralobular bronchioles break up into 18-20 terminal bronchioles with a diameter of about 0.5 mm. In the ciliated epithelium of the terminal bronchioles there are individual secretory cells (Clark), which produce enzymes that break down surfactant. These cells are also the source of restoration of the epithelium of the terminal bronchioles. All bronchi, starting from the main bronchi and including the terminal bronchioles, make up the bronchial tree, which serves to conduct a stream of air during inhalation and exhalation; respiratory gas exchange between air and blood does not occur in them.

65. Lungs: boundaries, structure, blood supply, innervation, regional lymph nodes.

The branching of the terminal bronchiole constitutes the structural unit of the lung, the acinus. The terminal bronchioles give rise to 2-8 respiratory (respiratory) bronchioles, and pulmonary (alveolar) vesicles already appear on their walls. Alveolar ducts extend radially from each respiratory bronchiole, blindly ending in alveolar sacs (alveoli). In the walls of the alveolar ducts and alveoli, the epithelium becomes single-layer flat. In the cells of the alveolar epithelium, a factor is formed that reduces the surface tension of the alveoli - surfactant. This substance consists of phospholipids and lipoproteins. Surfactant prevents the lungs from collapsing during exhalation, and the surface tension of the alveolar walls prevents excessive stretching of the lungs during inhalation. During forced inhalation, overstretching of the pulmonary alveoli is also prevented by the elastic structures of the lungs. The alveoli are surrounded by a dense network of capillaries, where gas exchange occurs. Respiratory bronchioles, alveolar ducts and sacs make up the alveolar tree, or respiratory parenchyma of the lungs. Person has 2 lungs - left and right. These are quite voluminous organs, occupying almost the entire volume of the chest, with the exception of its middle part. The lungs are shaped like a cone. The lower expanded part - the base - is adjacent to the diaphragm and is called the diaphragmatic surface. Corresponding to the dome of the diaphragm, there is a depression at the base of the lung. The narrowed, rounded upper part - the apex of the lung - extends through the upper opening of the chest into the neck area. In front it is located 3 cm above the 1st rib, in the back its level corresponds to the neck of the 1st rib. On the lung, in addition to the diaphragmatic surface, there is an external convex surface - the costal surface. On this surface of the lung there are imprints of the ribs. The medial surfaces face the mediastinum and are called mediastinal. In the central part of the mediastinal surface of the lung its gates are located. The gates of each lung include the primary (main) bronchus, a branch of the pulmonary artery that carries venous blood to the lung, and a small bronchial artery (a branch of the thoracic aorta), which carries arterial blood to nourish the lung. In addition, the vessels include nerves that innervate the lungs. Two pulmonary veins emerge from the gates of each lung, which carry arterial blood and lymphatic vessels to the heart. The bifurcation of the trachea, all the structural formations passing through the hilum of the lungs, and the lymph nodes together form the root of the lung. At the site of the transition of the costal surface of the lung to the diaphragmatic surface, a sharp lower edge is formed. Between the costal and mediastinal surfaces there is a sharp edge in front, and a blunt, rounded edge in the back. The lung has deep grooves dividing it into lobes. The right lung has two grooves that divide it into three lobes: upper, middle and lower; on the left - one, dividing the lung into two lobes: upper and lower. According to the nature of the branching of the bronchi and vessels in each lobe, segments are distinguished. In the right lung, there are 3 segments in the upper lobe, 2 segments in the middle lobe, and 5-6 segments in the lower lobe. In the left lung there are 4 segments in the upper lobe, 5-6 segments in the lower lobe. Thus, in the right lung there are 10-11, in the left there are 9-10 segments. The left lung is narrower, but longer than the right, the right lung is wider, but shorter than the left, which corresponds to the higher position of the right dome of the diaphragm due to the liver located in the right hypochondrium.

Blood circulation in the lungs has its own characteristics. Due to the function of gas exchange, the lungs receive not only arterial but also venous blood. Venous blood flows through the branches of the pulmonary arteries, each of which enters the gates of the lung and divides to the capillaries, where gas exchange occurs between the blood and the air of the alveoli: oxygen enters the blood, and from it carbon dioxide enters the alveoli. Pulmonary veins are formed from capillaries, carrying arterial blood to the heart. Arterial blood enters the lungs through the bronchial arteries (from the aorta, posterior intercostal and subclavian arteries). They nourish the wall of the bronchi and lung tissue. From the capillary network, which is formed by the branching of these arteries, bronchial veins are collected, flowing into the azygos and semi-gypsy veins, partly into the pulmonary veins from small bronchioles. Thus, the pulmonary and bronchial vein systems anastomose with each other.

Upper sections respiratory system are supplied by branches of the external carotid artery (facial, superior artery thyroid gland, lingual). The nerves of the lungs come from the pulmonary plexus, formed by the branches of the vagus nerves and sympathetic trunks.

The trachea, trachea (from the Greek trachus - rough), being a continuation of the larynx, begins at the level of the lower edge of the VI cervical vertebra and ends at the level of the upper edge of the V thoracic vertebra, where it is divided into two bronchi - right and left. The place where the trachea divides is called bifurcatio tracheae. The length of the trachea ranges from 9 to 11 cm, the transverse diameter is on average 15 – 18 mm.

Topography of the trachea.

Cervical region covered at the top by the thyroid gland, at the back the trachea is adjacent to the esophagus, and on the sides of it are the common carotid arteries. Except the isthmus thyroid gland, the trachea is also covered in front mm. sternohyoideus and sternothyroideus, except in the midline where the inner edges of these muscles diverge. The space between back surface the named muscles with the fascia covering them and the anterior surface of the trachea, spatium pretracheale, filled with loose fiber and blood vessels thyroid gland (a. thyroidea ima and venous plexus). Thoracic region The trachea is covered in front by the manubrium of the sternum, the thymus gland, and blood vessels. The position of the trachea in front of the esophagus is associated with its development from the ventral wall of the foregut.

Structure of the trachea.

The tracheal wall consists of 16 - 20 incomplete cartilaginous rings, cartilagines tracheales, connected by fibrous ligaments - ligg. annularia; each ring extends only two-thirds of the circumference. The posterior membranous wall of the trachea, paries membranaceus, is flattened and contains bundles of unstriated muscle tissue running transversely and longitudinally and providing active movements trachea during breathing, coughing and m. n. The mucous membrane of the larynx and trachea is covered with ciliated epithelium (with the exception of the vocal cords and part of the epiglottis) and is rich in lymphoid tissue and mucous glands.

Vessels and nerves.

The trachea receives arteries from the aa. thyroidea inferior, thoracica interna, as well as from rami bronchiales aortae thoracicae. Venous drainage is carried out into the venous plexuses surrounding the trachea, as well as (and especially) into the veins of the thyroid gland. The lymphatic vessels of the trachea along their entire length go to two chains of nodes located on its sides (peritracheal nodes). In addition, from the upper segment they go to the preglottic and upper deep cervical, from the middle to the last and supraclavicular, from the lower to the anterior mediastinal nodes.

The tracheal nerves originate from the truncus sympathicus and n. vagus, as well as from the latter’s vegwi – n. laryngeus inferior.

The main bronchi, right and left, bronchi principales (bronchus, Greek - respiratory tube) dexter et sinister, depart at the site of the bifurcatio tracheae almost at a right angle and are directed to the gate of the corresponding lung. The right bronchus is slightly wider than the left, since the volume of the right lung is larger than the left. At the same time, the left bronchus is almost twice as long as the right one; there are 6–8 cartilaginous rings in the right one, and 9–12 in the left one. The right bronchus is located more vertically than the left, and thus is like a continuation of the trachea. V. is thrown through the right bronchus in an arcuate manner from back to front. azygos, heading towards v. cava superior, the aortic arch lies above the left bronchus. The mucous membrane of the bronchi is identical in structure to the mucous membrane of the trachea.

In a living person, during bronchoscopy (i.e., when examining the trachea and bronchi by inserting a bronchoscope through the larynx and trachea), the mucous membrane has a grayish color; cartilaginous rings are clearly visible. The angle at the site of division of the trachea into bronchi, which looks like a ridge protruding between them, crista, should normally be located in the midline and move freely during breathing.

Skeletotopia. The projection of the lungs onto the ribs constitutes their boundaries, which are determined by tapping (percussion) or x-ray. The apices of the lungs are 3-4 cm above the collarbone, and at the back they reach the level of the spinous process of the VII cervical vertebra.
The anterior border of the right lung runs from the apex to the II rib along the linea parasternalis and further along the same line to the VI rib, where it passes into the lower border. The anterior border of the left lung in the 3rd rib runs the same way as the anterior border of the right, and in the 4th intercostal space it deviates to the linea medioclaricularis, from where it descends to the 6th rib and also passes into the lower border.

The lower border of the right lung crosses the 6th rib linea parasternalis 7 linea medioclavicularis 8 - linea axillaris media 9 linea axillaris posterior, 10 - along the line a scapularis, XI - along the linea paravertebral. The lower border of the left lung is located 1-1.5 cm below the right.
The posterior border of the right and left lungs runs from the apex to the 11th rib along the linea paravertebrals.

Syntopy. The subclavian artery is adjacent to the apex of the lung on the medial side. The costal surface, being covered with the parietal pleura, is separated behind the intrathoracic fascia from the intercostal vessels and nerves. The basis of the lungs lies on the diaphragm. In this case, the diaphragm separates the right lung from the liver, and the left from the spleen, left kidney and adrenal glands, stomach, transverse colon and liver.

The medial surface of the right lung in front of the hilum is adjacent to the right atrium; above - to the right brachiocephalic and superior vena cava; behind the gate - to the esophagus. The medial surface of the left lung in front of the hilum is adjacent to the left ventricle; above - to the aortic arch and the left brachiocephalic vein; behind the gate - to the thoracic aorta.
The topography of the root elements of the right and left lungs is not exactly the same. On the right, the main bronchus is located superiorly; below is the pulmonary artery; in front and below of which are the pulmonary veins. At the root of the left lung, the pulmonary artery lies above, below and behind it is the main bronchus, in front and below it are the pulmonary veins.

In front of the root of the right lung are the ascending aorta, superior vena cava, pericardium and part of the right atrium, above and behind is the azygos vein. The aortic arch is adjacent to the root of the left lung in front, and the esophagus is behind. The phrenic nerves run along both roots in front and the vagus nerves in the back.

In newborns, the lungs expand with the first breath. At the end of the 1st year of life, their volume increases 4 times; at the end of the 8th year - 8 times; at 12 years old - 10 times. The apex of the lungs in newborns reaches only the first rib, and the lower border is higher than in adults.
Blood supply lungs has its own characteristics. Arterial blood enters the lungs through the bronchial arteries, and venous blood flows out through the veins of the same name. In addition, venous blood enters the lungs through the pulmonary arteries. The pulmonary arteries are divided into lobar and segmental, which further branch according to the structure of the bronchial tree. Capillaries, having formed, entwine the alveoli. This ensures gas exchange between the air in the alveoli and the blood. Capillaries form venous vessels that carry arterial blood to the pulmonary veins. The systems of pulmonary and bronchial vessels are not completely isolated - there are anastomoses between their terminal branches.
Lymphatic vessels and nodes of the lungs. In the lungs there are superficial and deep lymphatic vessels. Superficial ones are formed from pleural lymphatic capillaries. Deep ones are formed from capillary networks around the terminal bronchioles, interacynary and interlobular spaces. The drainage lymphatic vessels pass through the regional lymph nodes, which are divided into:
1) pulmonary, nodi lymphoidei pulmonales, located in the parenchyma of the lungs, mainly at the sites of division of the bronchi;
2) bronchopulmonary, nodi lymphoidei bronchopulmonales, located in the area of ​​the hilum of the lungs;
3) upper tracheobronchial, nodi lymphoidei tracheohronchiales sup., lying along the trachea and the upper surface of the main bronchi;
4) lower tracheobronchial or bifurcation, nodi lymphoidei tracheobronchiales inf., located on the lower surface of the bifurcation of the trachea and main bronchi;
5) paratracheal, nodi lymphoidei paratracheales, located along the trachea.
Innervation The lungs are provided by branches of the vagus nerve, branches of the nodes of the sympathetic trunk, as well as branches of the phrenic nerve, which form the pulmonary plexus at the gates of the lungs, pl. pulmonalis. The pulmonary plexus is divided into anterior and posterior, its branches form the peribronchial and perivascular plexuses. Sensitive innervation of the lungs is carried out by cells of the lower node of the vagus nerve and cells of the lower cervical and upper thoracic spinal nodes. Nerve impulses from the bronchi are carried out mainly along the ferent fibers of the vagus nerves, and from the visceral pleura - along the ferent spinal fibers.
Sympathetic innervation of the lungs is carried out from the cells of the lateral horns throughout the Th II-V segments spinal cord. Parasympathetic innervation- from cells of the posterior nucleus of the vagus nerve. The axons of these cells reach the lungs as part of the branches of the vagus nerve.

Pleura, pleura, is the serous membrane of the lungs, which consists of a connective tissue base covered with mesothelium. There are two layers in the pleura: visceral (pulmonary) and parietal pleura, pleura visceralis (pulmonalis) et parietalis. The latter is divided into the mediastinal part, pars mediastinalis, which limits the mediastinum on the sides; costal, pars costalis, covering the chest wall from the inside, and diaphragmatic, pars diaphragmatica. At the lower edge of the lung root, the visceral pleura transforms into the parietal pleura and forms a fold - the pulmonary ligament, ligamentum pulmonale.
The slit-like space between the parietal and visceral pleura is called the pleural cavity, cavitas pleuralis. U healthy person this cavity is filled with 1-2 ml of serous fluid. At pathological conditions(pleurisy) the amount of fluid increases significantly. The latter is secreted by the free surface of mesothelial cells (mesothelial cells). Under normal conditions, mesotheliocytes also provide absorption of this fluid. In pathological conditions (pleurisy), the amount of fluid increases significantly, since the processes of excretion prevail over the processes of absorption. Between the different parts of the parietal pleura, three slit-like spaces are formed - pleural sinuses, recessus pleurales. The largest of them passes between the costal and diaphragmatic pleura - the costophrenic sinus, recessus costodiaphragmaticus. The second lies sagittally between the diaphragmatic and mediastinal pleura - the diaphragmatic-mediastinal sinus, recessus phrenicomediastinalis. The third is located vertically between the costal and mediastinal pleura - the costomedial sinus, recessus costo-mediastinalis. The pleural sinuses constitute the reserve spaces into which the lungs enter during maximum inspiration. With pleurisy, fluid accumulates primarily in the pleural sinuses, and later in the pleural cavity.
The level of the apexes of the pleural sacs (the dome of the pleura, cupula pleurae) coincides with the level of the apexes of the lungs.
The anterior border of the pleural sacs runs from the apex to the sternoclavicular joint. Further on the right it passes to the midline at the level of the angle of the sternum, from where it descends to the level of the VI-VII rib and passes into the lower border. On the left, at the level of the VI rib, the anterior border deviates laterally, then descends to the VI rib, where it becomes the lower border.
The lower border on the right along the linea medioclavicularis intersects the VII rib, along the linea axillaris media - IX, along the linea scapularis - XI, no linea paravertebral - XII. On the left, the lower border runs slightly lower.
The posterior border of the pleural sacs runs from the dome to the 12th rib along the linea paravertebral.

Mediastinum, mediastinum, is a complex of organs located between the mediastinal pleura. In front it is limited by the anterior chest wall; behind - the spine, necks of the ribs and prevertebral fascia; below - the diaphragm. The mediastinum is divided into: upper, mediastinum superius, and lower, mediastinum imferius, which in turn includes the anterior mediastinum, mediastinum anterius; middle, mediastinum medium, and back, mediastinum posterius. The border between the upper and lower passes along a conventional horizontal plane, which is drawn through the upper edge of the roots of the lungs. In the upper mediastinum lies the thymus or its remains, the ascending aorta and the aortic arch with its branches, the superior vena cava with its tributaries, the trachea, the esophagus, the thoracic duct, the sympathetic trunks, the vagus nerves, the trachea, the phrenic nerves, and the lymph nodes.

The anterior mediastinum is located between the body of the sternum and the pericardium. It includes fiber and processes of the intrathoracic fascia, in the leaves of which the internal thoracic arteries and veins, retrosternal and anterior mediastinal lymph nodes are located. The middle mediastinum contains the pericardium with the heart, the bifurcation of the trachea and the main bronchi, the pulmonary trunk, pulmonary arteries and veins, the phrenic nerves with the accompanying phrenic-pericardial vessels, and lymph nodes. The posterior mediastinum is located between the pericardium and the bifurcation of the trachea anteriorly and the spine posteriorly. It includes the descending aorta, vagus nerves, sympathetic trunks, esophagus, thoracic duct, lymph nodes and more.

1. The muscle that is on one side the thoraco-abdominal barrier, and on the other side the respiratory muscle:

A) diaphragm;

B) rectus abdominis muscle;

C) external oblique muscle;

D) transverse abdominal muscle;

E) serratus muscle.

2. Openings leading from the nasal cavity to the pharynx:

B) pharyngeal;

D) superior nasal passage;

E) sinus of the sphenoid bone.

3. The smallest branches of the bronchial “tree”:

A) lobar bronchi;

B) lobular bronchi;

C) terminal bronchioles;

D) segmental bronchi;

E) respiratory (respiratory) bronchioles.

4. Organ for coarse and fine air purification:

A) nasopharynx;

B) trachea;

C) bronchi;

D) nasal cavity;

E) larynx;

5. Opening from the oral cavity to the pharynx:

IN) Eustachian tube;

WITH) maxillary sinus;

D) jugular;

6. Part of the nasal cavity, which is called the olfactory cavity:

A) middle nasal meatus;

B) top;

C) lower;

E) external nose.

7. Main organs of the respiratory system:

A) bronchi;

B) pulmonary artery;

C) acicuses;

D) lungs;

E) alveoli.

8. Pressure in the pleural fissure:

A) 760 mm Hg;

B) – 9 mmHg;

C) 510 mm Hg;

D) above atmospheric;

E) – 19 mm Hg. Art.

9. Organ where the respiratory and digestive tracts intersect:

A) larynx;

B) pharynx;

C) esophagus;

10. The main respiratory muscles of a woman:

A) abdominal muscles;

B) diaphragm;

C) intercostal;

D) staircases;

E) serrated.

11. Distinctive feature of the human external nose in comparison with other vertebrates:

A) flattened;

B) protruding on the face;

C) depressed;

D) forked;

E) having two halves.

12. Average tracheal length:

A) 25 – 30 cm;

B) 40 – 41 cm;

C) 6 – 8 cm;

D) 5 – 10 cm;